The relationship of permittivity tensor of anisotropic medium in principal coordinate system and laboratory coordinate system is given. The characteristic of permittivity tensor of uniaxial anisotropic medium in the laboratory coordinate system is discussed. The transverse permittivity of an anisotropic plate is reconstructed in laboratory coordinate system based on the resonance and polarization characteristics of backscattering radar cross section (RCS) in wide band. Then, a new scheme of

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... nstructing the principal axis direction for a uniaxial sample plate is proposed, subject to the principal axis is unknown. The backscattering characteristics of a sample plate are discussed when the electromagnetic (EM) wave of different polarization is incident perpendicular to the sample plate. Three sample plates, which are cut perpendicularly to the x , y , and z axes in the laboratory coordinate system, are required. A numerical reconstruction example is given to demonstrate the availability of presented scheme. Corresponding author: B. Wei (bwei@xidian.edu.cn).